I'm using an 128x64 OLED display for my project but with a single page loading of OLED makes the compiler error of "size is too big".
How to use SD card as the RAM to display OLED using U8glib
PS:Things that to be displayed are taken from sensor module so please don't tell me about using progmem(Flash memory).
Thank u 
:o
I don't think that there is any kind of virtual memory available in the MCU (not only arduino) universe, and a SD card is too slow by orders of magnitude.
If your images are static you can create files in the SD using your PC and load them from your program.
I just start playing with u8g2 lib yesterday so I know far too little to teach how to do it, but I'm sure it can be done.
A compressed format like jpg is probably to much for a UNO or NANO but there are much simpler graphic formats that could be used.
I'm guessing that your problem is that there is too little memory on the Arduino, and u8g2 plus any libs you are using for access your sensors plus your code are using more than you have.
At the moment I'm close to have the same problem, only with the u8g2 lib, a temperature+humidity sensor and a real time clock.
Maybe there is a smaller and simpler OLED lib. I'd be happy only with fixed fonts, a draw and a plot function. For my project a lot of u8g2 is useless.
Good luck.
A monochrome 128x64 OLED only needs 1024 bytes to store a full screen image.
Most libraries use a 1k SRAM buffer for graphics. This enables you to plot individual pixels efficiently.
If you simply want to blit complete 128x64 images, there is no need for a buffer. You could blit them straight from Flash. And a Uno can store several 1k images in Flash.
If your application really does need more SRAM, buy an ESP8266 or ARM board. This would be easier than trying to add RAM to a Uno.
David.
Look at the teensy boards. This is what I've been using lately. The IDE can program them using the same stuff as your Arduino, but instead of 2k of RAM they have 64k. Makes WORLD of difference.
-jim lee